Yoshiya Ohnuma

A Novel Single-Phase Buck PFC AC–DC Converter With Power Decoupling Capability Using an Active Buffer

This paper discusses a new circuit configuration and a new control method for a single-phase ac-dc converter with power factor (P.F.) correction and a power pulsation decoupling function. The proposed converter can achieve low total harmonic distortion (THD) on the input current and the power pulsation decoupling function between the input and output sides, which allows low output voltage ripple even on a small output energy buffer at the same time using an active buffer. Therefore, the proposed converter does not require large smoothing capacitors or large smoothing inductors. The buffering energy is stored by a small capacitor, which controls the variation of the capacitor voltage through the active buffer. In this paper, the fundamental operations of the proposed converter are investigated experimentally. The experimental results reveal that the input current THD is 1.44%, the rate of the output voltage ripple is 6.33%, and the input P.F. is over 99%. In addition, a maximum efficiency of over 96% is obtained for a 750-W prototype converter.

A Single-Phase Current-Source PV Inverter With Power Decoupling Capability Using an Active Buffer

This paper proposes a new circuit configuration and a control scheme for a single-phase current source inverter with a power decoupling circuit which is called as the active buffer. The proposed inverter achieves low-DC-input voltage ripple and also provides sinusoidal current that can achieve unity power factor, without large passive components in DC bus such as smoothing inductors and electrolytic capacitors, which are conventionally required in order to decouple the power pulsation caused by single-phase power source. In this paper, the fundamental operations of the proposed inverter are demonstrated experimentally. From the experimental results, the input voltage ripple is 8.87% and the output current THD is 4.24%. In addition, the output power factor over of 99% and a maximum efficiency of 94.9% are obtained. Finally, it is confirmed that the maximum power density of the conventional circuit and the proposed circuit are 2.75 kW/L at the switching frequency 70 kHz and 4.86 kW/L at the switching frequency 80 kHz, respectively.

A control method for a single-to-three-phase power converter with an active buffer and a charge circuit

This paper proposes a new circuit configuration and a control method for a single-phase to three-phase power converter with power decoupling function. The proposed converter does not require a large reactor and large smoothing capacitors in the DC link part. Large smoothing capacitors are conventionally required in such converters to absorb the power ripple with a frequency that is twice of the power supply. The proposed topology is constructed based on an indirect matrix converter with an active buffer to decouple the power ripple. The buffering energy is kept by the voltage variation of the capacitor instead of its capacitance. In addition, the transfer ratio between the input and output voltage is obtained to 0.707 due to the connected charge circuit. In this paper, the fundamental operations of the proposed converter are confirmed by simulation and experiment results. As the experimental results, the input current THD and the output current THD are 3.17% and 3.64 %, respectively. The input power factor (P.F.) of over 99 % is obtained. In addition, the maximum efficiency of over 90.2% (input voltage = 100V) or 94.6 % (input voltage = 200V) is obtained by prototype.

Comparison of boost chopper and active buffer as single to three phase converter

This paper presents a comparison in terms of efficiency and volume between the single-to-three-phase power factor correction (PFC) converter. A conventional PFC circuit that consists of a boost chopper requires a large boost-up inductor and large smoothing capacitors to decouple the power ripple. The size and efficiency of the converter become a discussion issue recently. On the other hand, a single-to-three-phase power converter using an active buffer has been proposed. The active buffer does not require a large inductor and large smoothing capacitors in the DC link part. These two types of converters are designed and simulated to calculate the losses. In addition, a prototype converter has been built and tested. The efficiency achieves 94.6% at 1.5-kW same as the calculated efficiency. Furthermore, the efficiency increases by 1.5% comparing to the conventional converter. In addition, the volume is decreased by approximately 0.7 times then the size of the conventional converter.

Space vector modulation for a single phase to three phase converter using an active buffer

This paper proposes a space vector modulation scheme for a new single phase to three phase power converter that using an active buffer. The proposed circuit is based on the control theory of an indirect matrix converter which can successfully reduce the volume of the smoothing capacitor in the DC link part. The proposed circuit needs to control the output voltage and the buffer current at the same time. In order to reduce the output voltage and the input current harmonics, a space vector modulation scheme is proposed. In this paper, the basic operation of the proposed method is confirmed by experimental results. The input current THD and the output current THD around the fundamental component frequency are 3.34% and 6.65%, respectively. Moreover the capacitor current THD in the input filter and the output voltage THD that is below than 15 kHz switching frequency are improved by 10% and 17% because the switching waveforms becomes symmetrical shape. The validity of the proposed method is confirmed with these results.

Experimental verification of single-phase inverter with power decoupling function using boost-up chopper

This paper discusses a circuit configuration for a single-phase voltage source inverter that features power decoupling function. Generally, the converter that is connected to a single-phase power grid is required to decouple the power ripple with a twice frequency of the power grid. The proposed circuit compensates the single-phase power ripple by using an active buffer with small capacitors 50μF at 200 W. In this paper, the fundamental operations of the proposed converter are confirmed by experimental results. Then, the proposed converter is evaluated with the maximum power point tracking (MPPT) under a simulated photovoltaic (PV) conditions. From the experimental results, the output current Total Harmonic Distortion (THD) is 3.51% and the output power factor is over 99%. In addition, the input current ripple is reduced 12.3%. Moreover, from the loss analysis, the maximum efficiency of the inverter including the active buffer circuit is 95.5%.

Improvement of output voltage with SVM in three-phase AC to DC isolated matrix converter

This paper discusses and evaluates the performance of a 50-kVA three-phase AC to DC matrix converter. Comparing to the conventional converter, which consists of a PWM rectifier and an inverter, the matrix converter does not require a large reactor at the three-phase input side, and require no DC smoothing capacitor at the DC link part. A space vector modulation based on the virtual AC-DC-AC conversion with four-step commutation patterns is proposed for the converter. From the experimental results, the converter can obtain 2.49% THD on the input current and achieves approximately 91.4% efficiency at 40kW.

A novel single-phase buck PFC AC-DC converter using an active buffer

The present paper discusses a new circuit configuration and a new control method for a single-phase AC-DC converter with power factor correction (PFC) and a power pulsation decoupling function. The proposed converter can achieve low total harmonic distortion (THD) on the input current and the power pulsation decoupling function between the input and output side, which allows low output voltage ripple even on a small output energy buffer at the same time using an active buffer. Therefore, the proposed converter does not require large smoothing capacitors or large smoothing inductors. The buffering energy is stored by a small capacitor, which controls the capacitor voltage variation through the active buffer. In the present paper, the fundamental operations of the proposed converter are investigated experimentally. The experimental results reveal that the input current THD is 1.44%, the rate of the output voltage ripple is 6.33%, and the input power factor (P.F.) is over 99%. In addition, a maximum efficiency of over 96% is obtained for a 750-W prototype converter.

Control strategy for a three-phase to single-phase power converter using an active buffer with a small capacitor

A novel three-to-single-phase power converter that allows for smaller smoothing capacitors in the DC link is proposed. Large smoothing capacitors are conventionally required in such converters to absorb power ripple at twice the frequency of the single phase AC. The proposed topology consists of an indirect matrix converter and an active snubber to absorb the power ripple, and does not require a reactor or large smoothing capacitors. In this paper, the fundamental operation of the proposed converter is confirmed through simulations and experiments. The experimental results indicate that for a 1kW-class prototype circuit, the power ripple at twice the frequency of the power supply can be adequately suppressed using a buffer capacitor of only 50µF. Moreover, the single-phase power factor of over 99% and good waveforms for input and output current.

A single-phase current source PV inverter with power decoupling capability using an active buffer

This paper proposes a new circuit configuration and a control scheme for a single-phase current source inverter with a power decoupling circuit which is called as the active buffer. The proposed inverter achieves low-DC-input voltage ripple and also provides sinusoidal current that can achieve unity power factor, without large passive components in DC bus such as smoothing inductors and electrolytic capacitors, which are conventionally required in order to decouple the power pulsation caused by single-phase power source. In this paper, the fundamental operations of the proposed inverter are demonstrated experimentally. From the experimental results, the input voltage ripple is 8.87% and the output current THD is 4.24%. In addition, the output power factor over of 99% and a maximum efficiency of 94.9% are obtained. Finally, it is confirmed that the maximum power density of the conventional circuit and the proposed circuit are 2.75 kW/L at the switching frequency 70 kHz and 4.86 kW/L at the switching frequency 80 kHz, respectively.